Proposed fix: buildscript java version detection fails on Linux/Ubuntu on Picked up JAVA_TOOL_OPTIONS

[Kevin Rushforth]

David DeHaven wrote:
>> The gradle build tries to find the version of the used Java JDK by running 'java -version', skipping the first line and expects to find the version in the second line.
>>
>> However, on Linux (Ubuntu) the first line of *any* Java invocation is "Picked up JAVA_TOOL_OPTIONS: -javaagent:/usr/share/java/jayatanaag.jar"[1], thus failing at detection of the version, aborting the build.
>>
>> The 'Pickup up...' line is a standard feature of the JDK and a legacy that doesn't seem to be removed soon[2].
>>
>> I guess the build script needs to accommodate for this.
>>
>> Proposed fix:
>>
>> // Determine the verion of Java in JDK_HOME. It looks like this:
>> //
>> // $ java -version
>> // Picked up JAVA_TOOL_OPTIONS: -javaagent:/usr/share/java/jayatanaag.jar
>> // java version "1.7.0_45"
>> // Java(TM) SE Runtime Environment (build 1.7.0_45-b18)
>> // Java HotSpot(TM) 64-Bit Server VM (build 24.45-b08, mixed mode)
>> //
>> // The first line is optional, we need to parse the third line
>> def inStream = new java.io.BufferedReader(new java.io.InputStreamReader(new java.lang.ProcessBuilder(JAVA, "-version").start().getErrorStream()));
>> try {
>>    String v = inStream.readLine();
>>
>>    if (v != null) {
>> 	if (v.startsWith("Picked up")) {
>> 	   inStream.readLine();
>> 	}
>>
>>        v = inStream.readLine();
>>     
>
> Why not just use "java -fullversion" instead?
>
> $ java -fullversion
> java full version "1.8.0_60-ea-b14"
>
> $ JAVA_TOOL_OPTIONS="-Xmx512M" java -fullversion
> java full version "1.8.0_60-ea-b14"
>
> $ java -version
> java version "1.8.0_60-ea"
> Java(TM) SE Runtime Environment (build 1.8.0_60-ea-b14)
> Java HotSpot(TM) 64-Bit Server VM (build 25.60-b14, mixed mode)
>
> $ JAVA_TOOL_OPTIONS="-Xmx512M" java -version
> Picked up JAVA_TOOL_OPTIONS: -Xmx512M
> java version "1.8.0_60-ea"
> Java(TM) SE Runtime Environment (build 1.8.0_60-ea-b14)
> Java HotSpot(TM) 64-Bit Server VM (build 25.60-b14, mixed mode)
>
> It's a lot less stuff to parse. Also, "java -fullversion" does not start the VM, so should be faster.
>   

That makes sense as long as the output has everything we need. I need to 
make changes in this area anyway for JDK 9 in support of the new version 
string (JEP 223). See:

https://bugs.openjdk.java.net/browse/JDK-8133750

So this would seems like another good change to do, either as part of 
that fix or separately.

-- Kevin

> -DrD-
>
>